732 Knee, Ankle, and Foot Kinesiology

menisci hoop stress

as compression is applied, the external edge of the menisci expands outwardly bearing some of the stress. this stress is decreased if there is a tear in the meniscus

additional function of the menisci

• stabilize joint during motion

• lubricating articular cartilage

• provides proprioception, helping guide knee during arthrokinematics

knee motion in the frontal plane

there is no active control of the knee in the frontal plane; motion can occur but is due to external stresses placed on the knee

MCL

primary restraint to valgus force

LCL

primary restraint to varus force

ACL & PCL

as a group, the resist all motions of the knee providing multi-planar stability

function of the patella

acts as a pulley between the femur and quads to increase the moment arm of the knee extensors and changes direction of the quads line of pull

how does action at the quads impact the patella

contraction of the quads leads to compressive joint reaction force at the patellofemoral joint

how does increasing knee flexion angle impact the patella

increasing knee flexion angle during a squat increases compression force and the change in angle of muscle line of pull means a greater component of the QT and PF vector is directed at the joint surface

patella tracking during extension

during knee extension, the patella gets pulled superiorly, laterally, and posteriorly

lateral pull of patella

due to line of pull from the quads and IT band which can be assessed through Q-angle

posterior pull of patella

fibers of quad muscles pull patella into femur, which helps to stabilize the patellofemoral joint

optimal tracking

is when the movement between the patella and femur occurs across the greatest possible area of articular surface to decrease stress

abnormal tracking of patella

when the patella gets pulled too far laterally which can contribute to PF pain and potentially OA at the joint because it exposes the joint to higher stress

lateral directed forces on the patella

• force from IT band

• force from lateral patellar retinacular fibers

medial directed forces on the patella

• lateral facet of trochlear groove is steeper than medial→ bony block

• vastus medialis

• medial patellar retinacular fibers

knee alignment and patella

factors that increase valgus and/or axial rotation may increase the likelihood of abnormal lateral patellar tracking

bowstringing on patella

excessive knee external rotation and valgus during a dynamic movement; patella slides laterally as knee rotates internally

supination at the ankle

combination of plantarflexion, adduction, and inversion

pronation at the ankle

combination of dorsiflexion, abduction, eversion

subtalar joint pronation

eversion and abduction

subtalar joint supination

inversion and adduction

what is the transverse tarsal joint composed of as the most versatile joint of the foot

• talonavicular joint

• calcaneocuboid joint

movement at the transverse tarsal joint

rarely occurs in isolation and is associated with movement at the adjacent joint, especially the subtalar joint

transverse tarsal joint pronation

abduction and dorsiflexion

transverse tarsal joint supination

adduction and plantarflexion

when the foot is loaded, internal rotation of leg associated with…

• rearfoot pronation and eversion

• midfoot and forefoot supination

• arch drops/lowers

• valgus stress at the knee

when the foot is loaded, external rotation of the leg is associated with…

• rearfoot supination and inversion

• midfoot and forefoot pronation

• arch raises

• varus stress at the knee

windlass effect (or mechanism)

when standing on toes, passive tension is generated in the plantar fascia. This helps to raise and stabilize the arch

windlass mechanism on pes planus

less effective in a person with flat feet who has greater laxity/less stiffness in the plantar fascia which will likely manifest as a decreased ability to lift the heel when standing on toes

windlass mechanism pes cavus

In some highly rigid cavus feet, the plantar fascia is already under constant tension. This can either overwork the mechanism or hinder the necessary range of motion

alignment of the LE in a squat

healthy adults should be able to maintain alignment of the hip, knee, and ankle with the knee aligned approximately over the 2nd toe

alignment of the knee moving medial in a squat

• can be termed valgus collapse

• excessive hip medial rotation and/or adduction and excessive pronation of foot/ankle is observed

  • may be related to weak hip abductors or external rotators

alignment of knee moving over 2nd toe in a squat

• knee should not be too far in front of 2nd toe

• if too far, may led to increased compressive forces at the patellofemoral joint